Water Purification and Treatment

Natural Water Purification

• 1. Evaporation

• 2. Bacterial Action

• 3. Filtration

Purifying Water through the Hydrologic Cycle

Purifying Water through the Hydrologic Cycle

• 1. The sun provides energy for water to evaporate this resembles the process of distillation

• Evaporation leaves behind minerals, heavy metals, and other dissolved substances.

Purifying Water through the Hydrologic Cycle

• Water vapor condenses and falls as precipitation raindrops and snowflakes are nature’s purest form of water containing only dissolved atmospheric gases

• However, human activities release a number of gases into the air making today’s rain less pure than it used to be

Purifying Water through the Hydrologic Cycle

• 2. Bacterial Action• When raindrops strike the soil,

they collect impurities• But, as the water seeps through

the ground the bacteria in the soil feed on those impurities and repurify the water

Purifying Water through the Hydrologic Cycle

• 3. Filtration

• As water seeps further into the ground, it passes through gravel, sand, and rock

• This allows bacteria and suspended matter to be filtered out

Municipal Water Purification

• Major Steps• 1. Screening• 2. Prechlorination• 3. Flocculation• 4. Settling• 5. Sand Filtration• 6. Post chlorination• 7. Optional Further TreatmentRead article on pages 88-89 and define these terms

Chlorination of Water

• Read article on page 90 and outline the 3 methods of chlorination.

• What is a potential problem with water chlorination?

Chlorination and THM’s

• Ways to eliminate THM health risk• 1. Pass water through activated

charcoal filter.– Can get rid of THM’s but expensive to

install and operate.• 2. Use ozone or UV light instead of

chlorination– Won’t protect the water from

contaminants once it has left treatment plant

Hard Water

• Hard Water is water containing an excess of dissolved calcium (Ca2+) ions, magnesium (Mg2+) ions, or iron (III) (Fe3+) ions

• As water flows through limestone, chalk, and other rocks, these ions seep into the water

US Groundwater HardnessIs Your Water Hard or Soft?

How do we soften water???

• Water Softening Lab• 3 ways• 1. Sand Filtration• 2. Treatment With Calgon– http://www.youtube.com/watch?v=ZjNRXfRXnoc

• 3. Treatment with an Ion-Exchange Resin– http://www.youtube.com/watch?v=vCg-I5U9X3w